Chap. II.

COMPOSITION AXI) USE OF MINERALS.

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made hollow, so as to allow of a constant stream of water flowing through them to resistthe heat of the iron ; holes in the sides admit blasts of air, in the same way as in the blast-furnace. The pig-iron is laid in the refinery with the coke, and blasts of air passing throughthe flames are dashed against it, and the iron is melted; in about two hours or less, themetal is ready to he let of!'into a mould. In the process of refining a portion of the worstparts of the iron is left behind ; the chemical change is effected by a separation of a part ofthe carbon united to the pig-iron; when cooled the iron is broken into pieces of a manage-able size. Much less iron is now melted in the refinery than formerly, a method of con-verting pig-iron into malleable iron having been discovered without refining, which for manypurposes answers exceedingly well, and is more economical.

Malleable or Wrought-Iron -There are several kinds of pig-iron unfit for casting, but

which undergo other processes in order to be made into malleable or wrought-iron, whichis not brittle, like the former, and is so ductile that it can be drawn out to a considerablelength, and to the fineness of wire. It may be welded, that is, two or more pieces may behammered together into one : it is the iron ordinarily used by blacksmiths. For its con-version into malleable, the pig-iron has to he puddled, and then beat under the forge ham-mer, and passed through rolls or hollows in two iron cylinders, rolling round near to eachother, which force it into long bars; it is then cut into pieces by a pair of shears, the piecesare laid over each other, heated in a furnace, and again passed between the rollers, by whichit is forced into the shape intended.

Puddling Iron _To undergo this process the iron is put into a furnace, the fire being at

one end, and a chimney of sufficient height to produce a strong draught at the other. Theflames raised by the draught are drawn upon the iron, pass on, and the heated air goesup the chimney. In some iron works each puddling furnace has a chimney to itself, andtwentv or thirty or more such chimneys may be seen; but in others the air from all thepuddling chimneys is conveyed to one more lofty than the rest, creating a still strongerdraught. In about half an hour or less the iron becomes soft ; it is then heated until itis fluid, when it soon begins to boil. The puddler now stirs it with iron rods, bringingevery portion of the iron under the action of the Haines: after a time the boiling andfermentation cease, and the iron becomes thick and adhesive. The puddler now divides itinto parts, and rolls each part separately, until it has acquired something like the form of aball, when the pieces are taken out to be subjected to the action of the great forge hammer.The puddle furnaces, the forge hammers, and the puddle rolls are employed day and night,on account of the great labour and expense of fuel in heating the furnaces if allowed tocool, in order to bring them again into a fit state for working : two sets of hands are con-sequently required, who take the night and day work alternately.

Forging the Iron .—The iron being in ill-shaped masses, called balls one is taken from thepuddling furnace, by means of a rod of iron, with a sort of hook at the end, and is then laiddown to be forged, which is effected either by squeezing it forcibly between large pieces ofiron, worked by the steam-engine, called the squeezers , or subjecting it to the blows of theforge hammers, by which means the cinder mixed up with the pure iron is driven olfin ashower to a considerable distance, and a piece of iron is formed, somewhat resembling abrick, but from four to six times as large. This is immediately passed between the

Puddle Polls , two huge cylinders, in which are grooves, similar in shape to the mass itself,so that when they revolve the iron passes through them, and is squeezed into a longer form.A boy on the side opposite to the workman lays hold with the tongs of the end of theiron, and places the end which comes out last against the upper cylinder, the motion ofwhich carries it hack again to the side where the workman called the roller stands, whothen places the piece in the next groove, which as it passes through is still further elon-gated, and this process is repeated four times, when the iron becomes a bar, although a thickone. On a line with the two cylinders already mentioned are two others, their groovesbeing flat and broad, such as a bar may be laid upon, and there is a corresponding flatpiece of iron in the upper cylinder to press upon it.

The bar is now under the care of a second workman, who places it in the groove, throughwhich it passes and is elongated. It thus goes on through successive operations, becominglonger and more slender, until at last it is 10 or 12 feet long. It is then withdrawn, andlaid on a large flat piece of iron, and beaten by boys with wooden mallets, while it cools ;others stand by the bar, in order to keep it straight.

The usual method until lately was to puddle only the refined iron, or that which hadbeen smelted first in the blast furnace, and then again in the refining furnace. Of lateyears a practice has been introduced of puddling a mixture of pig-iron and refined iron, inStaffordshire called plate, thereby saving the expense of refining, and also the loss ofmetal always occasioned by that process; still greater economy is effected by dispensingwith the refined iron altogether, the loss upon which amounts to about 12. 1 , per cent.,which added to the expense of refining will make altogether a difference of 2 pounds perton. It is true that the iron so manufactured will not be so good, and may lose some-thing more in passing through the rolls, but for mo>t purposes it answers sufficiently